The purpose of this study is to explore the efficacy and safety of CsA ophthalmic gel in the treatment of moderate to severe dry eye disease .

A multicenter,randomized, double-blind, vehicle-controlled Study.Subjects will be randomly assigned to the experimental group and the control group,experimental group: CsA eye gel: 0.3 g: 0.15 mg, once daily;One drop into each eye when you use it.hypromellose eye drops:10ml：50mg,three times a day Control group: vehicle. One drop into the eye, once daily;One drop into each eye when you use it.hypromellose eye drops:10ml：50mg,three times a day

Inclusion Criteria:

1）18≤Age≤80, both male and female 2）According to the symptoms and signs and ophthalmologic examinations, the patients were diagnosed as moderate to severe dry eye

1. EDS score is more than 40 points;
2. BUT is less than 10 s;
3. Schirmer test result is less than 10mm/5 min;
4. ICSS≥2 points. 3）The ICSS score of baseline decreased by≤ 20% compared with that of screening period 4）Agree to participate in the study and voluntarily sign informed consent.

Exclusion Criteria:

1. Severe dry eye patients requiring surgical treatment
2. Had inner eye surgery within 12 months prior to screening or required inner eye surgery during the study period;Eyelid surgery was performed within 6 months prior to screening
3. Patients receiving permanent lacrimal insertion or patients receiving temporary lacrimal insertion within 6 months prior to screening;
4. Operation-induced dry eye
5. Glaucoma patients;
6. Unwilling to avoid wearing contact lenses;
7. Systemic inflammation or active eye infection and blepharitis;
8. Patients with multiple episodes of viral keratitis
9. Patients with ocular cicatricial pemphigoid, obvious conjunctival scar, ocular chemical burn and neurotrophic keratoconjunctivitis
10. Patients with malignant tumors in the past 5 years, except the thoroughly cured basal cell carcinoma of skin, squamous cell carcinoma in situ of skin, and primordial cervical cancer;
11. Perimenopausal women are taking hormone replacement therapy
12. Patients who cannot stop using other eye drops and other ophthalmic preparations during the study period;
13. Patients with severe cardiopulmonary diseases, uncontrolled hypertension and diabetes, etc. that affect the collection or compliance of study parameters;
14. ALT and AST ≥ 2 times of the normal upper limit, and serum creatinine ≥ 1.5 times of the normal upper limit
15. With a history of central nervous system disease or epilepsy, and/or a mental state that does not cooperate
16. Pregnant women and lactating women, or women of childbearing age, do not adopt effective contraceptive measures;
17. Participated in other clinical trials or participated in other clinical trials within 1 months before the election;
18. Systemic or topical cyclosporine drugs within 1 months before the election;
19. Allergy to CsA, fluorescein or any component of the drug is known；
20. Patients who were not considered suitable for the study, including those who were unable or unwilling to comply with the protocol requirements.